Optimization of alginate alkaline extraction technology from Sargassum latifolium and its potential antioxidant and emulsifying properties.

Alginate was recovered from Sargassum latifolium biomass using different conditions of alkali treatment. Box-Behnken experimental design was evaluated to study the influence of alkali:alga ratio, temperature and time on alginate yield, and its molecular weight (MW) and mannuronic/guluronic acid ratio (M/G). The second-order polynomial equations were analyzed by appropriate statistical methods. Extraction temperature and time were the most important factors during alginate alkaline extraction. MW and M/G ratio played an important role in controlling the reducing power of alginate. Increasing pH of the alginate solutions enhanced its reducing capacity, while thermal treatment showed a negative effect. Additionally, alginate exhibited good emulsion stabilizing capacities with diverse hydrophobic compounds. Emulsifying activity was less sensitive to temperature, ionic strength and more stable at acidic pH.